title: Anodic reactivity of ferrous sulfide precipitates changing over time due to particulate speciation.
abstract: The disposal of ferric phosphate (FePO4) sludge, routinely generated in wastewater and drinking water treatment, has a major impact on the overall treatment cost. Iron sulfide (FeSx) precipitation via sulfide addition to ferric phosphate (FePO4) sludge has been proven to be an effective method for phosphate recovery. Electrochemical oxidation of FeSx can then be utilized to recover ferric iron for reuse back in the phosphate removal process. In this study, the reactivity of FeSx particles for anodic oxidation at pH 4 was studied as a function of time after FeSx precipitate generation at a S/Fe molar ratio of 1.75. Cyclic voltammetry showed high reactivity for fresh FeSx particles, but the reactivity diminished significantly over a period of 1 month. X-ray absorption spectroscopy (XAS) revealed that this reduced reactivity with time is a consequence of the transformation of the FeSx particles in suspension from mackinawite (FeS) to pyrite (FeS2).
authors.affiliation: The University of Queensland , Advanced Water Management Centre (AWMC), St Lucia, Brisbane, Queensland 4072, Australia.
authors.forename: Elena
authors.initials: E
authors.lastname: Mejia Likosova
authors.forename: Richard N
authors.initials: RN
authors.lastname: Collins
authors.forename: Jurg
authors.initials: J
authors.lastname: Keller
authors.forename: Stefano
authors.initials: S
authors.lastname: Freguia
mesh_terms: D011232:Chemical Precipitation; D055664:Electrochemical Techniques; D004566:Electrodes; D005296:Ferrous Compounds / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D016018:Least-Squares Analysis; D017711:Nonlinear Dynamics; D052638:Particulate Matter / Q000737:chemistry*; D012995:Solubility; D013997:Time Factors; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005296:Ferrous Compounds; D052638:Particulate Matter; D006108:Graphite; D007501:Iron; C022597:ferrous sulfide